In 1983, a research and development effort relating to interior fuel gas piping systems was undertaken by the Gas Research Institute (GRI). The objective of this research and development effort was to identify and develop novel piping systems and materials that could serve as viable alternatives to conventional rigid black iron piping systems.
As a result of this effort, a piping system was developed that used semi-flexible, convoluted stainless steel tubing (CSST) in combination with elevated gas pressures of up to about 0.03 megapascals (MPa). This piping system offered marked advantages over rigid black iron piping systems. Included among these advantages were ease and speed of installation, elimination of the need for precise and time-consuming onsite measuring, cutting and threading of piping sections, and reduction of the need for certain fittings such as elbows, tees and couplings. One disadvantage that has been identified is increased flow resistance imposed by the tubing convolutions and by smaller internal diameters. This disadvantage has resulted in a requirement for higher system pressures and additional gas pressure regulators upstream of equipment requiring lower gas supply pressures.
Fittings that are conventionally used with CSST fuel gas piping, systems require the use of fiber sealing gaskets or the pre-flaring of the ends of the tubing. Fittings that require the use of fiber sealing gaskets are not completely reusable due to the fact that the gasket, which is mechanically compressed between (and possibly adhered to) the tubing and other fitting components, must be replaced. More importantly, the use of such fiber sealing gaskets is problematic in that such gaskets undergo gradual deterioration over time which compromises the integrity of the gas tight seal effected by such fittings.
One such prior art fitting is a fitting manufactured and sold by Ward Manufacturing, Blossburg, Pa., under the trade designation WARDFLEX.TM.. The WARDFLEX.TM. fitting, which is later described in detail, obviates the need for pre-flaring the ends of the tubing and is self-aligning to the extent that it aligns the tubing within the bore of an adaptor. However, the WARDFLEX.TM. fitting relies upon a fiber gasket to effect a gas tight seal and is not completely reusable. Moreover, this fitting does not serve to prevent the undesirable movement of the tubing jacket during installation and assembly nor does it serve to reduce or eliminate exposure of the tubing located within the fitting to contaminants or corrosive materials found in the surrounding environment.
One improvement over this prior art fitting is a fitting manufactured and sold by Mestek, Inc., Westfield, Mass., under the trade designation AUTOFLARE.TM.. The AUTOFLARE.TM. fitting is self-flaring and comprises: an adaptor, a steel collar inserted in the adaptor for alignment purposes, a nut and a brass split ring. Although the AUTOFLARE.TM. fitting does not employ a fiber sealing gasket it requires the use of a relatively small and hard to manipulate split ring that adversely impacts upon the ease of assembly. Moreover, this fitting also does not serve to prevent the undesirable movement of the tubing jacket during installation and assembly. In addition, it does not serve to reduce or eliminate exposure of the tubing located within the fitting to contaminants or corrosive materials found in the surrounding environment.
It is therefore an object of the present invention to provide a reusable fitting assembly that further facilitates the ease and speed of installation of semi-flexible piping systems.
It is a more particular object to provide a self-aligning and self-flaring fitting assembly that eliminates the need for sealing gaskets and that, when used with jacketed tubing, is capable of both preventing the undesirable movement of the jacket during installation and assembly and of reducing or eliminating exposure of the tubing located within the fitting assembly to contaminants or corrosive materials found in the surrounding environment.
It is a further object of the present invention to provide a hose assembly that employs such a fitting assembly.